In many circumstances in which valves are needed it is desirable to employ a valve whose operation occurs rapidly and without any throttling effect upon the fluid which is being controlled. Once valve operation has occurred, it is also desirable in many situations to have some assurance that the valve will not open or close except when valve operation is desired.
It is also desirable in certain operations to have a valve which will open or close within an upper and a lower limit and the value of such a valve is generally increased if the upper and lower operational limits are variable over wide ranges. The value of a valve is also increased if it can be converted from one type of operation to another.
The present invention has the previously mentioned desirable features and it provides valve apparatus which are capable of being used in normally closed, normally open, diverting, and manual reset modes or operational configurations.